I measured one at a local pick and pull last weekend, it measures 44"
center to center, spring perch. I don't know if you have to move the pads but that isn't much of a job compared to buying an a-body rear the last one I priced was $750. I was going to buy the Jeep $75 complete drum to drum, but everyone there had over 225k miles, seems like the Jeep owners get there miles out of them before they go the the salvage yard.
Hope this helps.
Bruce